Methods are known for fixing an elastic member or element such as an elastomeric band or ribbon to a flexible substantially inelastic web of material defining clothing or components thereof including briefs, panty briefs, disposable diapers and the like.
Methods are known for applying an elastic element to a continuously moving web. U.S. Pat. No. 3,828,367 to Bourgeois discloses a method for securing a stretched elastic element to a non-elastic fabric web and maintaining the assembled element on a web in a stretched condition until cut transversely in the direction of travel to produce separated panels. The apparatus is disclosed as including a rotating cylinder with a curved guide for imparting a non-linear configuration to the elastic element so that the ribbon follows a pre-determined contour of the non-elastic fabric.
U.S. Pat. No. 4,081,301 to Buell cites other prior art patents showing ways in which an elastic ribbon is joined to a moving web of material. The Buell patent itself discloses a method and apparatus for continuously attaching discrete lengths of elastic ribbon to a moving web. The elastic ribbon is fed in a stretched condition to the web and the elastic ribbon is intermittently secured to predetermined regions of the web while so stretched. Subsequently, the web and elastic ribbon are transversely cut in an area where the elastic ribbon is not secured to the web. This step forms severed unadhered portions of elastic at both ends of each discrete length of said elastic ribbon adhered to the web. The severed unadhered ends of the elastic ribbon are allowed to relax and contract to their unstretched state.
With the method disclosed in the above-discussed Buell patent, it is important that the moving elastic ribbon be secured to the moving web precisely at pre-determined regions of the web and that the moving elastic ribbon and moving web be severed precisely in the region where the elastic ribbon is not adhered to the web. This requires that the adhesive which is applied intermittently to the stretched elastic ribbon be precisely controlled for exact deposition combined with precisely controlling the placement of that exact area having adhesive thereon on the moving member. For example, if the adhesive is not put on correctly and the adhesive spaced correctly, the stretched elastic ribbon would be accidentally adhered beyond the pre-determined region and when then severed, the elastic ribbon would contract to impart an elasticized character beyond the desired pre-determined region. Thus, the securing mechanism such as the adhesive applicators, heat sealing devices, must be carefully controlled and actuated to effect securement precisely in the desired regions. With the very high speed manufacturing operations necessary for disposable product manufacture, accurate control of such mechanisms becomes difficult. Further, the securing mechanism is a movable device, and stresses imparted to the moving securing mechanism increase owing to the more rapid acceleration and deceleration which necessarily occur in high-speed stop and start operations. Furthermore, the intermittent application of either a liquid or semi-solid adhesive in fine lines through small orifices or nozzles is difficult. The continual stopping and starting of the ejection of adhesive through the nozzles causes the nozzles to clog or stop-up during use, thus causing considerable down-time and loss of production.
In order to avoid the problems of precisely and accurately registering ribbon securing mechanisms in a high-speed operations, the imposition of high stress on moving mechanical members and the possible clogging of nozzles, it would be desirable to provide a method and apparatus in which the securing mechanism or adhesive is disposed continuously and uniformly throughout the operation. With such a method, the securing means is operated along the entire length of the elastic member so as to avoid the problems associated with high-speed cyclic operation.
Further, in accordance with our new and improved method, the relative positioning of the various components making up a stretch disposable diaper, that is, one that has elastic on the leg portion of the diaper, is no more complicated than the problem of the relative positioning of the components of a standard or flat disposable diaper. In its broadest aspects, the invention of our new and improved method for inserting elastic members into disposable diapers is to control the shape of the absorbent panel and thereby control the positioning and securement of the elastic member in the diaper.